Insulation for the Farmhouse - The Initial Discussions

We have a pot of 3 options (below) for insulating the gigantic old farmhouse, but we're struggling to get reliable advice on which way to go. There is absolutely no consensus online or offline, so not screwing up this part is a bit harder.

Solid walls are always tricky to insulate for reduced energy consumption, and with the scale of this huge property, the decision-making is even tougher. The complex shape makes all options difficult, but we need to pick the best way forward within the next week or two.

On the table is:

➡️ Option 1: External Wall Insulation (EWI) onto the solid wall (stone)

➡️ Option 2: Internal subframe with all modern materials inside

➡️ Option 3: Internal VPM (breathable) boards and/or lime-based insulating plaster

(if we missed one, please shout it out!)

The main factors to mull over are the exposed stone internally, plus many original features lost in Option 2 and 3, vs external fabric disruption from Option 1 - oh, and the cost!).

If you have experience with any of these three, we'd really appreciate a comment with your thoughts before the end of April 2024 🙏

(Not insulating isn't an option for us, and with the climate changing, we need to try to future-proof a little bit where possible)